1. Field of the Invention
This invention relates to injection devices and in particular, but not exclusively, to reusable autoinjector devices comprising a housing into which a disposable syringe may be inserted to effect the injection and then removed and replaced as required for the next injection.
2. Description of the Related Art
It is a common requirement that autoinjectors signal to the user when the injection is complete by means of an ‘injection complete’ signal. The term ‘injection complete’ is used to refer to a condition in which a satisfactory delivery of the drug has been achieved. It is also desirable that this indication is not only visual but also audible and/or tactile, to provide confirmation to the user when injection site is out of sight, or would require some straining to see, for example in the buttocks or upper arm.
It is desirable that at least some of the energy required to generate the audible signal is stored in an energy store associated with an indicator element so that a fast impact energetic movement can be released, that is essentially independent of the actual speed of plunger movement. Moreover it is desirable to provide an indicator arrangement which resets automatically for each injection cycle.